Conductors, Insulators, and Semiconductors Quiz

Study Notes

Materials can be classified into three groups based on their conductivity: conductors, insulators, and semiconductors.
Conductors have high electrical conductivity. Examples include copper, silver, and aluminum (metals).
Insulators have very low electrical conductivity. Examples include glass, wood, and mica.
Semiconductors have conductivity between conductors and insulators. Their conductivity depends on temperature. Examples include Germanium (Ge) and Silicon (Si).

In solids, atoms are close together, and the energy levels of their outermost electrons are affected by neighboring atoms.
This interaction leads to slightly different energy levels for electrons in the same orbit.
These different energy levels group together to form energy bands.
The valence band corresponds to the energy levels of valence electrons.
The conduction band is the lowest unfilled energy band.
The forbidden energy gap is the energy difference between the top of the valence band and the bottom of the conduction band.

Conductors have an overlapping valence and conduction band, meaning there is no forbidden energy gap.
Electrons can easily move from the valence band to the conduction band, leading to high conductivity.
Insulators have a large forbidden energy gap ($E_g > 5$ eV) between the valence and conduction bands.
The valence band is completely filled, and the conduction band is empty. Electrons cannot jump to the conduction band, resulting in very low conductivity.
Semiconductors have a smaller forbidden energy gap than insulators, but larger than conductors.
The conductivity of semiconductors can be increased by adding impurities (doping).